This is a continuing long-term project in which a large number of nondiabetic relatives of diabetic patients, as well as asymptomatic mildly diabetic patients, are being studied periodically. In addition to detecting early defects in carbohydrate metabolism, we are seeking to find parameters, other than those associated with carbohydrate metabolism, which will indicate the existence of the early diabetic states. Methods by which the evolution from prediabetes to subclinical diabetes, from subclinical diabetes to latent chemical diabetes, and from latent asymptomatic diabetes to overt diabetes can be modified, are being sought. Young patients with latent (asymptomatic or chemical) diabetes have been studied prospectively for periods of up to 22 years and will continue to be studied to ascertain possible changes in (1) carbohydrate metabolism, (2) insulin secretion, (3) glucagon secretion, (4) growth hormone secretion and (5) the possible evolution of microangiopathy, macroangiopathy and neuropathy. BIBLIOGRAPHIC REFERENCES: Fajans, S. S. Weissman, P.N., Floyd, J.C., Jr., Williamson, J.R., Vogler, N. J., Kilo, C., and Conn, J. W.: Studies on the Natural History of Asymptomatic Diabetes in Young People. In: Various Faces of Diabetes in Juveniles. Mod. Probl. Paediat. Vol 12, Jerusalem Academic Press and S. Karger AG (Basle) eds., pp. 7-17, 1975. Tattersall, R.B. and Fajans, S.S.: A Difference Between the Inheritance of Classical Juvenile-Onset and Maturity-Onset Type Diabetes of Young People. Diabetes 24:44-53, 1975.